1. Technical Field
The invention relates to technology for forming a detection image and detecting the detection image by a plurality of detectors.
2. Related Art
An image forming apparatus for forming a latent image by exposing a photosensitive member surface by an exposure unit and forming an image by developing the latent image is known. For example, an image forming apparatus disclosed in Japanese Patent No. 2642351 or JP-A-2004-347999 forms desired images by successively forming linear latent images extending in a direction substantially orthogonal to a moving direction of a surface of a photosensitive drum by means of an exposure unit while moving the surface of the photosensitive drum in a specified direction. In the apparatus of Japanese Patent No. 2642351 and JP-A-2004-347999, a color image is formed by superimposing images of a plurality of colors formed as described above.
In such an image forming apparatus, there are cases where a plurality of detectors are provided, detection images are formed for the respective detectors and information on image formation is obtained from the detection results on the detection images by these plurality of detectors. For example, an image forming apparatus disclosed in Japanese Patent No. 2642351 obtains color misregistration information necessary for color image formation by forming detection images for a plurality of different colors (“detection pattern” of Japanese Patent No. 2642351). More specifically, this apparatus forms detection images of different colors for the formation of a satisfactory color image by properly superimposing toner images of the respective colors. The detection images are detected by optical sensors and the positions of the detection images are obtained from the detection results. The color misregistration information is obtained from the thus obtained positions of the detection images of the respective colors. Further, the apparatus disclosed in Japanese Patent No. 2642351 includes two optical sensors and forms the detection images for each optical sensor. The color misregistration information is obtained from the detection results on the detection images by the two optical sensors.
Further, an image forming apparatus disclosed in JP-A-2004-347999 forms detection images (“registration marks” in JP-A-2004-347999) to obtain information on color misregistration resulting from the tilt (skew) of an exposure unit relative to a photosensitive drum. Specifically, two optical sensors are arranged side by side in a direction orthogonal to a moving direction of a drum surface, and the detection images are formed for each optical sensor. The information on color misregistration resulting from the skew is obtained from the detection results of the respective optical sensors.
As described above, in the apparatuses disclosed in Japanese Patent No. 2642351 and JP-A-2004-347999, a plurality of detectors are provided, the detection images are formed for each detector, and the information on image formation is obtained from the detection results on the detection images by these plurality of detectors.